1. Field of Invention
The present invention relates to a device for controlling a color video display. The device according to the present invention is used, for example, for video apparatuses, and television recording and display apparatuses or the like.
2. Description of the Related Arts
In general, in a device for controlling a display in a video apparatus, three-phase clock signals (.phi..sub.1 , .phi..sub.2 , .phi..sub.3) are produced from the two phase clock signals (.phi..sub.1 (fs), .phi..sub.2 (fs)) or three times the frequency clock signal on the basis of a signal having a reference frequency which is twice the frequency fs of the subcarrier, which is equal to 3.58 MHz. By combining the produced three phase clock signals , .phi..sub.1, .phi..sub.2 , .phi..sub.3) having predetermined amplitudes with predetermined phase differences, various color signals and a color burst signal are produced to obtain a composite video signal.
In prior art devices for controlling a display in a video apparatus, however, a problem arises in that the generation of signals having precise phase differences therebetween cannot be ensured. Also, a problem arises in that the amplitudes of color signals cannot be changed, and therefore, the display of a correct color at a desired position along a horizontal scanning line cannot be made. Also, a problem arises in that the display according to the PAL system using a three phase clock signal having a frequency which is three times the subcarrier frequency, cannot be carried out.